Receiving "An unexpected error has occurred." after selecting classification node on advanced search page in Windchill PartsLink

• Receiving a Windchill Error with code 501 on Advanced Search when selecting Part type on Advanced Search page
• Receiving Windchill Error "An unexpected error has occurred." after selecting a specific classification node on Advanced Search page
• Below error popup when clicking Classification Explorer 

  An unexpected error has occurred.  Contact your system administrator for assistance

• Windchill Error with code 501 occuring on Advanced Search when specific classification node is selected
• When searching inside a classification, user gets the error below on Advanced Search page:

  Windchill Error
  Contact your administrator for assistance. Information for their reference follows.
  Request Id:        <customer specific request ID>
  Request URI:      /PDMLink/ptc1/queryBuilder
  Query String:     typeChanged=true
  Status Code:      501
  Message:            An unexpected error has occurred. Contact your system administrator for assistance.

• Error in the Method Server Log:

com.ptc.mvc.controllers.ExceptionController xxx- message : Cannot invoke "com.ptc.core.lwc.common.view.ConstraintDefinitionReadView$RuleDataObject.getEnumDef()" because "<localxx>" is null
error:-------------wt.util.WTException: Cannot invoke "com.ptc.core.lwc.common.view.ConstraintDefinitionReadView$RuleDataObject.getEnumDef()" because "<localxx>" is null wt.util.WTException: Cannot invoke "com.ptc.core.lwc.common.view.ConstraintDefinitionReadView$RuleDataObject.getEnumDef()" because "<localxx>" is null
	at com.ptc.windchill.enterprise.search.mvc.controllers.AngularQueryBuilderController.doWork(AngularQueryBuilderController.java:179)
	at com.ptc.windchill.enterprise.search.mvc.controllers.AngularQueryBuilderController.renderQueryBuilder(AngularQueryBuilderController.java:66)
	at jdk.internal.reflect.GeneratedMethodAccessor1134.invoke(Unknown Source)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:568)
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205)
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:150)
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808)
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1072)

ERROR com.ptc.windchill.enterprise.search.mvc.helpers.AngularQueryBuilderHelper USER_Name - Exception while creating the QB attribute Json String from attrInfoCollection
ERROR com.ptc.mvc.controllers.ExceptionController USER_Name - message : An unexpected error has occurred.  Contact your system administrator for assistance.
error:-------------wt.util.WTException wt.util.WTException
	at com.ptc.windchill.enterprise.search.mvc.controllers.AngularQueryBuilderController.doWork(AngularQueryBuilderController.java:173)
	at com.ptc.windchill.enterprise.search.mvc.controllers.AngularQueryBuilderController.renderQueryBuilder(AngularQueryBuilderController.java:66)
	at jdk.internal.reflect.GeneratedMethodAccessor2789.invoke(Unknown Source)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190)
	...